For example, cantilever or center-pull caliper brake devices comprise a pair of brake arm mounts fixed to the fork of a bicycle and each having a pivot, a pair of brake arms movably supported by the respective pivots, and return springs each provided between the brake arm and the mount. Each return spring has its opposite ends held to the brake arm and the mount for biasing the brake arm to position a brake shoe attached to the arm away from the rim of the wheel.
Unexamined Japanese Utility Model Publication SHO 63-992 and the specification of U.S. Pat. No. 4,754,853 disclose assemblies for adjusting the force of the return spring.
According to the prior art, the return spring is held at its one end to the mount side and at the other end thereof to a coupling member on the brake arm side. The coupling member is adjustable by rotating an adjusting screw provided on the brake arm to thereby remedy one-sided action of the brake or adjust the tension (return spring force).
The return spring may be adjusted merely by advancing or retracting the adjusting screw, with the other end of the return spring bearing on the forward end of the adjusting screw. However, if the return spring is merely in bearing contact with the adjusting screw at their opposed ends which are flat, it is likely that one end will be displaced laterally from the other end to render the spring unadjustable. It is therefore useful for reliable adjustment to provide the coupling member as in the prior art.
Nevertheless, the coupling member is rotatable relative to the brake arm and is in face-to-face contact therewith, so that the member encounters very great frictional resistance, becomes difficult to rotate and is likely to break the adjusting screw.
An object of the present invention is to provide an assembly for adjusting the force of a return spring for use in bicycle brake devices wherein an adjusting screw is provided at its forward end with a socket portion having the end of the return spring directly fitted therein to overcome the problem of the prior art.